Electromagnetic circuit breaker with roller type latch



Nov. 30, 1965 A. R. NORDEN ETAL 3,

ELECTROMAGNETIC CIRCUIT BREAKER WITH ROLLER TYPE LATCH Filed April 22, 1963 5 Sheets-Sheet 1 ACTUATING ACTUATING FORCE FORCE l TRIPPING FORCE 7 i 4:. 1,5 (we? INVENTORS ALEXANDER R NORDEN BY CARL F. BRUNNER Www- ATTORNEY Nov. 30, 1965 A. R. NORDEN ETAL 3,221,121

ELECTROMAGNETIC CIRCUIT BREAKER WITH ROLLER TYPE LATCH Filed April 22, 1963 5 Sheets-Sheet 2 ACTUATING FORCE INVENTORS ALEXANDER R. NORDEN BY CARL F. BRUNNER wfwyk ATTORNEY Nov. 30, 1965 A. R. NORDEN ETAL 3,221,121

ELECTROMAGNETIC CIRCUIT BREAKER WITH ROLLER TYPE LATCH Filed April 22, 1963 5 Sheets-Sheet 5 CONTACT PRESSURE e.-: 54 40/ INVENTORS ALEXANDER R. NORDEN BY CARL F BRUNNER ATTOR Nov. 30, 1965 A. R. NORDEN ETAL ELECTROMAGNETIC CIRCUIT BREAKER WITH ROLLER TYPE LATCH Filed April 22, 1963 5 Sheets-Sheet 4 ATTORN Y Nov. 30, 1965 A. R. NORDEN ETAL ELECTROMAGNETIC CIRCUIT BREAKER WITH ROLLER TYPE LATCH 5 Sheets-Sheet 5 Filed April 22, 1963 IN VENTORS ALEXANDER R NORDEN BY CARL F. BRUNNER United States Patent Oftice 3,221,121 Patented Nov. 30, 1965 York Filed Apr. 22, 1963, Scr. No. 274,685 15 Claims. (Cl. 200106) This invention relates to electromagnetic circuit breakers or the like. The invention is principally characterized by a novel trippable linkage which is more accurate and more reliable than those of this type heretofore known in the art and by a novel contact arm assembly in which a single spring provides both opening pressure and contact pressure for a set of contacts. The invention is also characterized by other novel features as set forth in the description which follows.

Electromagnetic circuit breakers are devices which automatically open an electrical circuit in the event of an unsafe overload. As a rule, the circuit breaker is normally set by closing the electrical contacts of the circuit breaker through a trippable mechanical linkage, which is automatically tripped when an unsafe overload condition arises, thereby opening the contacts. In certain electromagnetic circuit breakers, the tripping force is provided by current passing through a coil in series with the electrical contacts and a magnetic tripping member which applies pressure to the trippable linkage depending on the strength of the magnetic field generated by the current passing through the coil. The magnetic field strength, of course, is a function of the current flow through the coil, and the trippable linkage is adapted to trip at a prede termined current value related to time. A reset mechanism is provided to reset the circuit breaker after it has been tripped by an overload condition.

Many circuit breakers of the above described type have been devised in the past, but they have all suffered certain disadvantages, the most notable of which were associated with the trippable linkage and contact arm assemblies. In many circuit breakers, the trippable linkage would occasionally trip prematurely or fail to trip on its rated overload. In addition, the trippable linkage often required a relatively large tripping force. Furthermore, the prior art linkages which were reasonably reliable and accurate tended to be critical with respect to the dimensions and fit of the individual parts, which led to a high percentage of rejects in low cost, mass produced circuit breakers.

The contact arm assemblies of the prior art circuit breakers also suffer from certain disadvantages. When the contacts are closed, it is necessary to have a positive contact pressure to hold the contacts closed against electrodynamic forces and also to reduce contact resistance. It is also necessary, however, to have the contacts spring loaded to the open position so that they will automatically open when the trippable linkage is tripped. In the past, relatively complex contact arm assemblies with multiple spring loading were required to achieve these conditions. The contact opening spring, of course, increased the cost of the circuit breaker and decreased, by biasing the contacts in the opening direction, the net available contact closing force.

Accordingly, one object of this invention is to provide a trippable mechanical linkage which permits a decrease in the required tripping force.

A further object of this invention is to provide a contact arm assembly in which a single spring provides both opening pressure and contact pressure for a set of contacts.

An additional object of this invention is to provide a trippable mechanical linkage which is not critical with respect to the dimensions and fit of the individual parts and which is therefore Well suited for use in circuit breakers produced at low cost by mass production methods.

Other objects and advantages of the invention will become apparent to those skilled in the art from the following description of several specific embodiments, thereof, as illustrated in the attached drawings, in which:

FIG. 1A is a schematic elevation view of a prior art trippable linkage;

FIG. 1B is a plan sectional view taken on the line B-B of FIG. 1A;

FIG. 1C is a magnified elevation view of the roller shown in FIGS. 1A and 1B;

FIG. 2 is a schematic elevation view of another prior art trippable linkage;

FIG. 3A is a schematic elevation view of one trippable mechanical linkage of this invention;

FIG. 3B is a plan sectional view taken on the line BB of FIG. 3A;

FIG. 4A is a schematic elevation view of one contact arm assembly of this invention in its fully open position;

FIG. 4B shows the contact arm assembly of FIG. 4A with the contacts about to touch;

FIG. 40 shows the contact assembly of FIG. 4A with contact pressure applied to the contacts;

FIG. 5A is an elevation sectional view of one circuit breaker of this invention in the open position;

FIG. 5B is an elevation sectional view of the circuit breaker of FIG. 5A in the closed position; and

FIG. 5C is a plan section taken on the line C-C of FIG. 5B.

The trippable mechanical linkage of this invention can be best described in connection with the prior art trippable linkages shown in FIGS. 1A, 1B, 1C, and 2. Referring to FIG. 1A, the prior art trippable linkages contained two movable members 10 and 12 which make contact with each other via a roller 14. Movable member 10 is adapted to move downwardly in response to an actuating force and to roll off roller 14 in response. to :a tripping force. Movable member 12 is adapted to slide up and dowa in guide channels (FIG. 1B) which are engaged by the axle 16 of roller 14. A spring 20 urges member 12 up Wardly, so that it will return to its rest position, as indicated by the dashed lines in FIG. 1A, when member 10 is tripped.

In the above described prior art linkage, member 12 is coupled to a movable contact arm or the like, and the arm is moved from a first position to a second position when the actuating force is applied to member 10. When a tripping force is applied to member 10, it rolls oil roller 14 and allows the arm to return to its first position under the influence of spring 20. In this mechanism, the roller 14 is provided to reduce the amount of tripping force required to trip the mechanism. Roller 14, however, also introduces unreliability into the mechanism because it tends to trip accidentally when the actuating force is applied. As the axle 16 of roller 14 moves down into its guide channel, it contacts the sides of the channels and develops a torque which tends to roll member 10 ofii, thereby tripping the mechanism. The problem of accidental tripping is also present when movable member 12 is guided entirely by separate guide pins rather than by axle 16. In this case a roll-oh torque is developed by vibration and other random forces. To counteract this roll-01f torque, it has been necessary in the past to bias the mechanism toward the untripped position. This was done by inclining the axis of member 10 toward the untripped position, or by tapering the bottom of member 10 as shown in FIG. 2, thereby urging the mechanism toward its untripped position when the actuating force was ap-' plied.

Both of these prior art arrangements nullified the tendency to accidental tripping, but they were self defeating in the sense that they also increased the amount of force required to trip the mechanism. In other words, although the roller acted to reduce the tripping force requirements, it encouraged accidental tripping, which was overcome in the past by a bias force that increased the tripping force requirements. In accordance with this invention, however, a novel mechanism has been devised which overcomes the tendency to accidental tripping without any increase in the tripping force requirements.

One illustrative embodiment of this invention is illustrated schematically in FIGS. 3A and 3B. In this invention, roller 14 is journaled on a pivot arm 22 which applies an anti-tripping torque to roller 14 when the mecha nism is being actuated but not when it is stationary in the actuated position. Pivot arm 22 is guided at one end by a channel (FIG. 3B) and at the other end by a pair of pivot blocks 24 and 26. An arm 28 is journaled to pivot arm 22 to actuate a movable contact arm or the like. Arm 28 is spring loaded to its upward position by spring means which are not shown in the drawings. When an actuating force is applied to member 10, roller 14 is driven downward, and as it moves downward, a counterclockwise torque is applied by the rotation of pivot arm 22. The counterclockwise torque drives arm towards its untripped position, thereby nullifying any tendency of accidental tripping. It should be noted that pivot arm 22 will also move back and forth in a thrust motion between pivot blocks 24 and 26 if the guide channel shown in FIG. 3B is straight rather than arched. After the mechanism has been moved to its downward position, as indicated by the dashed lines in FIG. 3A, the anti-tripping torque disappears, because it is due to the motion of pivot arm 22, which ceases when the mechanism reaches its downward position. Member 10 can then be tripped by a small force.

It will be understood by those skilled in the art, of course, that the trippable linkage of this invention is by no means limited to the particular embodiment illustrated in FIGS. 3A and 3B. The pivot arm 22 might, for example, be a Y shaped member rather than an L shaped member, with the roller being secured in the crotch of the Y by a separate axle member. The arm 22 might also be a T shaped member with two rollers employed, one in each leg of the top bar of the T member. In addition, the movement of the roller could be guided by arm 28 rather than by pivot arm 22, with the anti-tripping torque still provided by the pivot arm as shown.

The structure shown in FIGS. 3A and 3B is but one example of the trippable linkage of this invention.

FIGS. 4A through 40 show the contact arm assembly of this invention in schematic. In FIG. 4A, a contact arm 30 carrying a contact 32 is pivoted around a fixed pivot 34 and spring loaded to its open position by an expansion spring 36. When an actuating force is applied to the end of the arm, it pivots around pivot 34 and moves contact 32 into contact with a stationary contact 38 to make an electrical circuit. When the actuating force is released, spring 36 moves the contact arm back to its open position, which is limited by a fixed abutment member 40. The novel action of this contact arm is provided by an oversize opening in contact arm 30 to receive fixed pivot 34. After the contacts 32 and 38 have met, contact arm 30 will be disengaged from fixed pivot 34 as indicated in FIG. 4C. When contact arm 30 is disengaged from pivot 34, the force of expansion spring 36 will act to press contacts 32 and 38 together rather than apart. When the actuating force is removed, how ever, spring 36 will move contact arm 30 upward until it engages pivot 34 again, whereupon the force of spring 36 will be translated into a contact opening force and will produce a snap opening action of the contacts. The snap opening feature results from the fact that the contact arm is moving upwardly when the force of spring 36 is translated from a contact closing force to a contact opening force. This can be better appreciated by noting the relative positions of contact arm 30 and pivot 34 in FIGS. 4C and 4B respectively. FIG. 4C shows the fully closed position. When the actuating force is released, contact arm 30 will be drawn upwardly, but the force of spring 36 will still be pressing contacts 32 and 38 together as arm 33 moves upward. Contacts 32 and 38 will, in fact, act as a pivot for arm 39 in this phase of its travel. Therefore, the arm 30 will be in motion before any contact opening force is applied to the contacts, which means that the contacts are subjected to a rocking action, which results in forces tending to break or pry apart any light welds of contacts, thus assuring dependable opening of the circuit. In other words, the lost motion between the arm 30 and pivot 34 also results in a definite prying action at the contacts and an inertia energy, both of which tend to break any slight welding or sticking of one contact to the other.

FIGS. 5A, 5B, and 5C show an electromagnetic circuit breaker which incorporates the above described trippable linkage and contact arm assembly of this invention. This circuit breaker is an improvement of the circuit breaker described in US. Patent Number 2,890,306, which was issued on June 9, 1959, to A. B. Rypinski et al. for an Electromagnetic Circuit Breaker. Referring to FIGS. 5A and 5B, the circuit breaker is contained in a molded plastic case C comprising two matching halves C and C (FIG. 5C). The case will not be described in detail, since it is essentially the same as the case disclosed in the above noted U.S. patent. Mounted on the top of the case is a manual handle 42 which closes electrical contacts 44 and 46 via a trippable linkage and contact arm assembly comprising a top armature 48, a side armature 52, a roller 54 and pivot arm 56, and a contact arm 58. Side armature 52 is spring loaded to its upward position by a torsion spring 50, and contact arm 58 is spring loaded to its open position by an expansion spring 60. Contact arm 58 rotates about a fixed pivot 62, which engages an oversized hole 64 cut into arm 58. Actuating force is applied to the end of the arm from roller 54 via a mechanical link 66, which is journaled to pivot arm 56 at one end and rigidly secured to contact arm 58 at the other end by machine screws.

The circuit breaker is thrown from its open position (FIG. 5A) to its closed position (FIG. 5B) by manually moving handle 42, which has a cammed lower surface that forces top armature 48 downward. Top armature 48 in turn forces side armature 52 downward, which forces roller 54 downward and moves contact arm 58 to its closed position. Under unsafe overload conditions, side armature 52 will be tripped off roller 54 by a tripping armature 70 which is actuated by the magnetic field from coil 72. Tripping armature 70 is a generally L shaped member which is slotted in the bottom surface of the L to receive the bottom of side armature 52 and which is rockably supported between the sides of case C by means of ears E which engage sockets formed in the sides of case C. Tripping armature 70 is normally held in its untripped position by a small torsion spring 74, which is adapted to engage tripping armature 70 at one end and to engage one of a plurality of adjustment pegs 76 at the other end. Pegs 76 are provided as adjustments for the amount of force necessary to move tripping armature 70 from its untripped to its tripped position. By moving the end of spring 74 from one peg to another, the force applied to tripping armature 70 can be increased or decreased as desired. Tripping member 70 is, of course, made of a magnetic material which will be attracted to the core of coil 72 by the magnetic field generated by the current flow therethrough. When tripping member 70 has been moved far enough, it will push side armature 52 off roller 54 and allow the contacts 44 and 46 to be opened by spring 60, as indicated by the dotted lines in FIG. 5B. After the mechanism has been tripped,

it is reset by handle 42 returning to the OFF position (FIG. 5A), thus allowing torsion spring 50 to return side armature 52 to its normal position above roller 54. When handle 42 is subsequently returned to its ON position, contacts 44 and 46 will be closed again and will remain closed until the trippable mechanism is tripped by another overload or handle 42 is returned manually to its OFF position.

The details of handle 42, top armature 48, spring 50, side armature 52, tripping armature 70, spring 74, and coil 72 will not be discussed further in this document, since these parts of the circuit breaker are the same as those shown in the above noted US. Patent No. 2,890,306. The details of the contact arm assembly and roller-pivot mechanism, however, are more fully disclosed in FIG. 50, which shows pivot arm 56 slidably engaged at one end in a slot 78 formed in case section C1 and retained in place at the bend therein by an abutment 80 formed in case section C2. The other end of pivot arm 56 is guided between two pivot blocks 82 and 84, which are formed in case section C2. Pivot blocks 82 and 84 are adapted to permit both a pivotal and sliding movement of pivot arm 56, which occurs due to having a straight slot 78 rather than an arched slot. The invention, of course, is by no means limited to the specific pivot structure disclosed in FIGS. 5A, 5B and 5C, but this particular structure has been found to be preferable in circuit breakers of the type disclosed herein. In other circuit breakers, however, it may well be desirable to modify the pivot structure and also the contact arm structure for one reason or another.

The above disclosed circuit breaker can be adapted to trip at any desired current level by proper selection of the number of turns in coil 72 and by proper adjustment of spring 74, as will be apparent to those skilled in the art. The adjustment pegs 76 for spring 74 provide enough variation to compensate for normal mass production tolerances.

From the foregoing description, it will be apparent that this invention provides a trippable mechanical linkage which is more reliable and more sensitive than those heretofore known in the art, without the need for critically accurate dimensions and fits. It will also be apparent that this invention provides a contact arm assembly in which a single spring furnishes both opening pressure and contact pressure for a set of contacts. And it should be understood that this invention is by no means limited to the specific structures disclosed herein by way of example, since many modifications can be made in the disclosed structure without departing from the basic teaching of this invention. For example, the pivotal connection for the contact arm need not necessarily comprise a pivot member engaging a hole in the contact arm; it could comprise a pivot member attached to the contact arm engaging an enlarged hole in the case of the circuit breaker. These and many other modifications of the disclosed structure will be apparent to those skilled in the art, and this invention includes all modifications falling within the scope of the following claims.

What is claimed is:

1. In an electrical circuit breaker, a trippable linkage comprising roller means, means for linearly limiting said roller means between a first and a second position, a force transmitting member in contact with said roller at the periphery thereof, and movable with said roller means between said first and second positions thereof, tripping means for disengaging said force transmitting member from said roller means by movement transverse to the linear movement of said roller means, and anti-tripping means for applying a torque to said roller means to oppose disengagement of said roller and force transmitting means only while they are being moved from said first to said second positions.

2. The combination defined in claim 1 wherein said roller means comprises a roller, and an axle coupled to said roller.

3. The combination defined in claim 2 wherein said anti-tripping means comprises means for rotating said axle during the linear movement of said roller to oppose disengagement of said roller and force transmitting means.

4. The combination defined in claim 3 wherein said anti-tripping means comprises a pivot arm coupled at one end to said axle, said pivot arm being pivoted about a fixed point at the other end thereof for rotating said axle during said linear movement to oppose disengagement of said roller and force transmitting means.

5. The combination defined in claim 4 in which said axle and pivot arm comprise a unitary member, wherein said means for linearly limiting said roller means comprises a channel engaging one end of said axle to define said linear movement thereof.

6. In an electrical circuit breaker containing a fixed contact and a movable contact, the improvement comprising: a contact arm coupled to said movable contact; pivot means having a predetermined later-a1 play coacting with said contact arm and disposed to bring said movable contact into contact with said fixed contact when said contact arm is rotated in a first direction; spring means normally urging said movable contact away from said fixed contact; trippable actuating means for pivoting said contact arm in said first direction to close said contacts and disengage said pivot means from said contact arm when said contacts are closed whereby said spring means urges said movable contact towards said fixed contact; said trippable actuating means comprising roller means, means for linearly limiting said roller means between a first and second position, means for coupling said roller means to said contact arm for closing said contacts when moved from said first to said second position, a force transmitting member in contact with said roller means at the periphery thereof and movable therewith between said first and second positions, tripping means for disengaging said forced transmitting member from said roller means by movement transverse to the linear movement of said roller means, and anti-tripping means for applying a torque to said roller means to oppose disengagement of said roller and force transmitting means only while they are being moved from said first to said second positions.

7. The combination defined in claim 6 wherein said roller means comprises a roller, and an axle coupled to said roller.

8. The combination defined in claim 7, wherein said anti-tripping means comprises means for rotating said axle during the linear movement of said roller to oppose disengagement of said roller and force transmitting means.

9. The combination defined in claim 8 wherein said anti-tripping means comprises a pivot arm coupled at one end of said axle, said pivot arm being pivoted about a fixed point at the other end thereof for rotating said axle during said linear movement to oppose disengagement of said roller and force transmitting means.

10. The combination defined in claim 9 in which said axle and pivot arm comprises a unitary member, and in which said means for linearly limiting said roller means comprises a channel engaging one end of said axle to define said linear movement.

11. The combination defined in claim 10 in which said movable contact is located on said contact arm on one side of said pivot means and said spring means acts against said contact arm on the other side of said pivot means.

12. The combination defined in claim 11 in which said trippable actuating means acts against said contact arm on said other side of said pivot means and wherein the distance from said pivot means to said trippable actuating means is greater than the distance from said pivot means to said spring means.

13. The combination defined in claim 12 wherein said pivot means comprises a pivot pin engaging a hole in said contact arm and wherein said hole is significantly larger than said pivot member, thereby allowing said pivot member to disengage from said contact arm when said contacts are closed.

14. The combination defined in claim 13 and also including means for tripping said trippable mechanism in response to a predetermined level of current flow through said contacts, thereby opening said contacts.

15. The combination defined in claim 14 and also References Cited by the Examiner UNITED STATES PATENTS 2,876,308 3/1959 Christensen 200-88 2,890,306 6/1959 Rypinski et a1. 200-88 X BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner. 

1. IN AN ELECTRICAL CIRCUIT BREAKER, A TRIPPABLE LINKAGE COMPRISING ROLLER MEANS, MEANS FOR LINEARLY LIMITING SAID ROLLER MEANS BETWEEN A FIRST AND A SECOND POSITION, A FORCE TRANSMITTING MEMBER IN CONTACT WITH SAID ROLLER AT THE PERIPHERY THEREOF, AND MOVABLE WITH SAID ROLLER MEANS BETWEEN SAID FIRST AND SECOND POSITIONS THEREOF, TRIPPING MEANS FOR DISENGAGING SAID FORCE TRANSMITTING MEMBER FROM SAID ROLLER MEANS BY MOVEMENT TRANSVERSE TO THE 